SANTA CLARA, Calif. — Colin Kaepernick and the San Francisco 49ers have conquered the bitter cold of Green Bay and the travails of a cross-country flight to Carolina.

Now they face their toughest test yet to get back to the Super Bowl: the deafening noise of Seattle's 12th man home crowd and that swarming Seahawks defense that thoroughly shut down the reigning NFC champion Niners in Week 2.